diff --git a/src/Plugin/migrate/process/EntityLookup.php b/src/Plugin/migrate/process/EntityLookup.php
index 8d6f496..ea62ed9 100644
--- a/src/Plugin/migrate/process/EntityLookup.php
+++ b/src/Plugin/migrate/process/EntityLookup.php
@@ -174,7 +174,7 @@ class EntityLookup extends ProcessPluginBase implements ContainerFactoryPluginIn
           case 'entity_reference':
             if (empty($this->lookupBundle)) {
               $handlerSettings = $fieldConfig->getSetting('handler_settings');
-              $bundles = array_filter((array) $handlerSettings['target_bundles']);
+              $bundles = array_filter((array) ($handlerSettings['target_bundles'] ?? []));
               if (count($bundles) == 1) {
                 $this->lookupBundle = reset($bundles);
               }